The present invention relates to a process for producing polyolefins having special rheological and compatibilization properties, as well as to the resulting polyolefins and to their use.
The problems that arise with polymers in general, and polyolefins in particular, relate to their insufficient melt strength when they are being processed by extrusion.
It is well known that the melt strength of polyethylene (PE) and of polypropylene (PP), which is defined by a high elongational viscosity, is insufficient in certain types of processing, such as extrusion foaming, extrusion blow-moulding, thermoforming and blow moulding, particularly 3D blow moulding.
Solutions proposed for solving this problem consist in making the macromolecular structure of the PE or PP branched by creating covalent bonds between the macromolecules. However, in practice, branched resins manufactured by covalent coupling all suffer from a tendency of the branches to degrade due to the effect of shear inherent in the processing. Moreover, significant irreversible covalent branching results in melt fractures, limiting the productivity and/or quality of the finished product.
In order to be able to increase the connection density between macromolecules without being limited by crosslinking, it is possible to provide a substantial pert of the branches via reversible ionic bonds. This makes it possible to increase the melt strength while retaining the thermoplastic character.